Effect of sugarcane expansion on bacterial communities in sandy and clayey soils

Soil microbial communities play a key role in ecosystem functioning and are highly sensitive to land-use change. This study evaluated alterations in soil microbial communities induced by the expansion of sugarcane cultivation over extensive pasturelands in Manduri and Brotas, São Paulo state, Brazil, characterized by clayey and sandy soils, respectively. A synchronic approach based on land-use chronosequences was adopted, including native vegetation (NV), degraded pasture (PA), plant cane (CAp), ratoon cane (CAs), and, in sandy soil, ratoon cane with straw retention (CAs-p). Soil samples were collected at depths of 0–10, 10–20, and 20–30 cm.

Bacterial, fungal, and archaeal abundances were quantified by qPCR targeting the 16S (Bacteria and Archaea) and 18S (Fungi) rRNA genes. Bacterial community structure was assessed by T-RFLP of the 16S rRNA gene and analyzed using NMDS ordination based on Bray–Curtis distances and non-parametric tests. Bacterial abundance decreased with land-use change and soil depth (p < 0.01), with the lowest values observed in CAs-p (−2.83 ± 1.23; p = 0.02). Fungal abundance was not affected by land use (p > 0.05) but declined with depth (p = 0.003). In contrast, archaeal abundance increased in sugarcane areas, particularly in CAp and CAs-p (p < 0.05), and in deeper soil layers. NMDS revealed clear differentiation of bacterial community structure among soil textures and land uses, with native vegetation forming distinct clusters.

Overall, sugarcane expansion over pasturelands alters soil microbial abundance patterns and bacterial community structure, with responses strongly modulated by soil texture and depth.